Gregory had the power of healing by laying on of his hands. Often the healing was so powerful that the patient was cured of his illness, and became a fervent convert on the spot.

During the construction of a church for his growing flock, the builders ran into a problem with a huge buried boulder. Gregory ordered the rock to move out of the way of his church; it did.

In order to stop the River Lycus from its frequent and damaging floods, Gregory planted his staff at a safe point near the river bank. He then prayed that the river would never rise past the staff. The staff took root, grew into a large tree, and the river never flooded past it again. This act led to his patronage against floods and flooding.

Two local pagans, hearing that Gregory was a soft touch for money, decided to con the bishop. One lay beside the road where Gregory was travelling, and pretended to be dead. The other stopped the bishop, pleaded poverty, and asked for money to bury his dead friend. Gregory had no money with him, so he took off his cloak and threw it over the “dead” man, telling the “live” one to sell the cloak and use the funds. When Gregory had moved on, the “live” con-man found that his friend had died.

Two brothers in Gregory’s diocese had inherited a piece of land that contained a lake. Unable to decide how to divide the lake, the two settled on armed combat to settle the matter. On the night before the battle, Gregory prayed for a peaceful solution to the matter. The next morning the brothers found that the lake had dried up leaving easily dividable farm land.

During Gregory’s time in the desert during the Decianpersecutions, an informer told the authorities where to find the bishop. Guards went to the site, but found nothing but two trees standing in isolation in the desert. The informer went back to the place and found that what the soldiers had seen as trees were actually Gregory and a deacon in prayer. This convinced the informer of the reality of Gregory’s God, and he converted.

When returning from the wilderness, Gregory had to seek shelter from a sudden and violent storm. The only structure nearby was a pagan temple. Gregory made the sign of the cross to purify the place, then spent the night there in prayer, waiting out the storm. The next morning, the pagan priest arrived to receive his morning oracles. The demons who had been masquerading as pagan gods advised him that they could not stay in the purified temple or near the holy man. The priest threatened to summon the anti–Christian authorities to arrest Gregory. The bishop wrote out a note reading “Gregory to Satan: Enter”. With this “permission slip” in hand, the pagan priest was able to summon his demons again.

The same pagan priest, realizing that his gods unquestioningly obeyed Gregory’s single God, found the bishop and asked how it was done. Gregory taught the priest the truth of Christianity. Lacking faith, the priest asked for a sign of God’s power. Gregory ordered a large rock to move from one place to another; it did. The priest immediately abandoned his old life, and eventually became a deacon under bishop Gregory. This ordering about of boulders led to Gregory’s patronageagainst earthquakes.

There is one God, the Father of the living Word, who is His subsistent Wisdom and Power and Eternal Image: perfect Begetter of the perfect Begotten, Father of the only-begotten Son. There is one Lord, Only of the Only, God of God, Image and Likeness of Deity, Efficient Word, Wisdom comprehensive of the constitution of all things, and Power formative of the whole creation, true Son of true Father, Invisible of Invisible, and Incorruptible of Incorruptible, and Immortal of Immortal and Eternal of Eternal. And there is One Holy Spirit, having His subsistence from God, and being made manifest by the Son, to wit to men: Image of the Son, Perfect Image of the Perfect; Life, the Cause of the living; Holy Fount; Sanctity, the Supplier, or Leader, of Sanctification; in whom is manifested God the Father, who is above all and in all, and God the Son, who is through all. There is a perfect Trinity, in glory and eternity and sovereignty, neither divided nor estranged. Wherefore there is nothing either created or in servitude in the Trinity; nor anything superinduced, as if at some former period it was non-existent, and at some later period it was introduced. And thus neither was the Son ever wanting to the Father, nor the Spirit to the Son; but without variation and without change, the same Trinity abideth ever. – a declaration of faith by Saint Gregory